observation
LoadingGlobal temperature
HadCRUT5 · anomaly relative to 1850–1900
Can natural factors explain the warming?
The Sun, volcanoes and ocean fluctuations affect climate. The question is whether they explain the long-term rise in global temperature. Here we compare their development over time and their assessed contributions to warming.
Three series, separate units
Choose a year. The markers move together across all charts. Each series keeps its own scale: similar-looking lines alone do not establish a cause.
1950197520002025
Solar activity
LoadingSolar irradiance
NOAA TSI · model-based annual mean at the top of the atmosphere
Internal variability
LoadingEl Niño / La Niña
NOAA Niño 3.4 · mean of twelve monthly values
The solar series is a model-based NOAA climate dataset, not a satellite-only measurement. The Niño index describes sea-surface temperature in the tropical Pacific, not global temperature.
What would we expect to see?
Is the Sun the main cause?
If more solar energy drove the long-term rise, its influence would have to increase accordingly over recent decades. The series shows solar-cycle fluctuations, but no matching long-term increase. Stronger sunlight would also warm the stratosphere; it has cooled.
NASA: the Sun and warmingWhat do volcanoes do?
Major eruptions inject sulfate aerosols into the stratosphere. They reflect sunlight and can cool Earth for several years. This explains temporary deviations, but not a temperature trend rising over decades.
NASA GISS: volcanic aerosolsCan El Niño explain the warming?
El Niño and La Niña redistribute heat between the ocean and atmosphere. They strongly affect individual years. As internal variability, however, they do not add a lasting new source of energy to the climate system.
NOAA: Niño 3.4 dataWhat about orbital cycles?
Changes in Earth's orbit affect climate over many thousands of years. Their pace and current direction do not match the rapid temperature rise since the 20th century.
NASA: orbital cyclesHow much of the warming do these factors explain?
The IPCC assesses the change in global surface temperature in 2010–2019 relative to 1850–1900. The bars show uncertainty ranges in °C; they are not a time series through 2025.
−0.3 °C0 °C+0.5 °C+1.0 °C+1.5 °C
Observed
+1.06 °C
Human influence
+1.07 °C
Sun and volcanoes
−0.1 to +0.1 °C
Internal variability
−0.2 to +0.2 °C
The ranges describe uncertainty in each estimate. Observation and contributions are different quantities; their central values should not be read as exactly additive individual measurements.
IPCC AR6, Figure SPM.2Interim finding
Natural influences are real, but do not explain the long-term rise
Die Messreihen zeigen Schwankungen; die IPCC-Bewertung trennt deren Beiträge vom langfristigen menschlichen Einfluss. Der nächste Schritt prüft, wie dieser Einfluss unabhängig nachgewiesen wird.
Data and methods
NOAA TSI Climate Data Record v03r00NOAA NCEI / LASP
Annual model-based solar irradiance · 1950–2025 · W/m²
NOAA Niño 3.4NOAA Physical Sciences Laboratory
Monthly values · aggregated to annual means · 1950–2025 · °C
HadCRUT5Met Office Hadley Centre / Climatic Research Unit
Global temperature anomaly · 1950–2025 · 1850–1900 reference
IPCC AR6, SPM.2Intergovernmental Panel on Climate Change
Assessed contributions to warming in 2010–2019 relative to 1850–1900